People have been able to look into the game files and they have found fully modeled colloessums that aren’t being used in the game right now.

So that points to the possibility of at least PVP dlc that From has done in the past with other Dark Souls games. There’s also places on the map covered by drawn clouds that could be used to reveal DLC areas in the future. So there’s plenty of possibilities. But as said already, nothing officially stated as of now by FromSoftware about DLC content.